Multiple layers of silicon–silica (Si–SiO2) pair onto silicon substrate towards highly efficient, wideband silicon photonic grating coupler

A single mode waveguide grating coupler based on multiple Si–SiO2 pairs onto Si substrate has been designed. Numerical analysis has been carried out to calculate optimum thickness of the layers of Si–SiO2 that ensures the constructive interference between reflected waves and actual guided wave for high coupling efficiency. Based on the results, an optimal design is developed and modeled by using a 2-D finite difference time domain simulator that dictates a coupling efficiency of as much as 78 % (−1.07 dB) at the wavelength of 1550 nm, and a 1-dB bandwidth of 77 nm. The numerical method will be useful to calculate the optimum thicknesses of the layers for any reflector based grating coupler of different materials.